Cream the sugar and butter in a bowl. Add the flour, baking powder, salt and eggs and beat well.
Spoon the batter into a springform pan of 8,9 or 10 inches. Place the plum halves skin skin up on top of the batter. Sprinkle lightly with sugar and lemon juice, depending on the sweetness of the fruit. Sprinkle with about 1 tsp of cinnamon, depending on how much you like cinnamon.
Bake 1 hour, approximately. Remove and cool; refrigerate or freeze if desired. Or cool to lukewarm and serve plain or with whipped cream. (to serve a torte that was frozen, defrost and reheat it briefly at 300 degrees.) To freeze, double wrap the torte in foil, place in a plastic bag and seal. Yield 8 servings.
